Divergent consequences of different biochar amendments on carbon dioxide (CO) and nitrous oxide (NO) emissions from the red soil.

Climate change due to greenhouse gas (GHG) emissions is one of the global environmental matters of the 21st century. Biochar (BC) amendments have been proposed as a potential solution for improving soil quality and to mitigate GHGs emissions. Therefore, we evaluated the influence of different BCs on soil CO and NO emissions in an outdoor pot experiment. The soil was mixed with three different types of BCs; bamboo, hardwood, and rice straw BCs as BB, BH, and BR, respectively, and control as B0 with four levels (0, 5, 20, and 80 g kg of soil). Gas samples were collected on a bi-monthly basis for six months. A polyvinyl chloride (PVC) static chamber was placed on each replicate to collect the gas samples at 15, 30, 45, and 60 min, respectively. Compared to B0, the lowest cumulative NO emissions were observed in BH80 (11%) followed by BH20, BH5, and BR80. However, for cumulative CO emissions, B0 and BC treatments showed no significant differences except for BB80 (>11%) and BB5 (<2%). BC type and level both had a significant (P < 0.001) impact on the cumulative NO emissions with a significant interaction (P < 0.001). However, cumulative CO emissions were unaffected by BC type but BC level showed a significant influence on cumulative CO emissions (P < 0.05) and there was a significant (P < 0.001) interaction between the BC type and level on cumulative CO emissions. Overall, higher doses of BR and BB showed a pronounced effect on soil pH over BH. The soil pH and moisture showed a negative correlation with NO emissions whereas soil temperature showed a positive correlation with the cumulative fluxes of NO. Our results demonstrate that BC incorporation to soil may help to mitigate GHGs emissions but its influence may vary with BC type and level under different conditions and soil type.